Bladders can leak. Hopefully mine never will. But they aren't nearly as sensitive to operation on rough bumpy runways as wet wings - especially when the sealant gets old. But there is a safety issue that is seldom mentioned .... if you have to put her down off runway and bend a wing, you are more likely to spew fuel out with a bent wet wing than with a bladder. The wing can deform and split open at a seam, but with bladders the fuel can still be contained, giving you time to get out of harms way. But if a wet wing seam splits and gallons of fuel are released things can possibly turn out much worse.
I love my bladders, but I understand they may not be the best choice for everyone. I didn't care about the weight because I never put humans in the back of my C and never get near gross weight. I sealed the tanks on my first Mooney back in the 80s myself. I will never, ever do that again!